As is well known, such can-like packages have primarily been used up to now for accommodating powdery material or dry products. In this case, the container body frequently consists of wound paper or cardboard material which can be produced with very exacting tolerances as regards wall thickness and diameter. Thus, it is possible to close the container with a sheet by means of heat-sealing. The sheet used is usually made of composite material, e.g., aluminum/plastic. Since the edge end surface of the container member does not suffice for a sufficiently firm and tight seal seam, the sheet has to be placed in a U-shape on the container edge and sealed with the inner container surface and/or the outer container surface. The container closed in such a way can additionally be covered with a reclosable cover.
With very exacting tolerances, e.g., below 0.5 mm for the diameter of the container edge, integral seal heads moving into the container edge may be used for sealing. In this case, it is possible to produce a seal seam having sufficient strength and gas-tightness. Although an internal seal can also be achieved with dimensional tolerances above 0.5 mm, this is only possible by means of an expanding seal arbor. Although sufficient mechanical strength can optionally be obtained therewith, the danger exists that less tightly sealed areas are formed at the junctures of the expanding arbor elements, so that an absolutely gas-tight connection cannot be guaranteed between the parts.
In addition, such packages are also used for contents which are to be sterilized. In this case, the connection between the container parts has to have a particularly high mechanical strength so as to receive the different pressures occurring during sterilization without any problems.
In other fields of application, extraordinary great demands are made on the hermetic seal, particularly in the case of oxygen-susceptible package contents.
The object of this invention is to further develop a package having features such that the indicated problems and drawbacks are avoided and high mechanical connecting strength and particularly high gas-tight hermetic connection can be achieved, also for containers, whose bottom edge openings are subject to major dimensional fluctuations, e.g., above 0.5 mm.
This problem is solved by providing a closure for the open end of a container having a small thickness, the closure being made of a sealable or weldable sheet material connected to the edge of the open container end in a mechanically resistant and hermetically sealed manner by heat sealing or welding to an area of the container which is inclined relative to the axis of the container. In general, the connection area between the container and the closure is divided into at least two different areas, one of which is primarily developed as a mechanically resistant connecting area, and the other is primarily developed as a hermetically sealed connecting area.
It is essential to assign the seal connection to an inclined surface.
Due to the division of the seal connection into two different areas, attention can be focused on either sufficient mechanical strength or gas-tight hermetic seal in each seal area by process control and geometrical configuration. In the area of high strength, microchannels or the like may be tolerated, since a hermetic seal is effected in the other areas. It will not be required for these areas to achieve the desired resistance to pressure if it is ensured that these hermetically sealed areas are relieved or saved from possible, increased internal pressures or the like by the other areas of increased seam strength. In many cases, one seal surface will already be sufficient if it is arranged conically over a relatively large surface.
The seal surface area of an inner edge surface which has an inclination predetermined as compared to the container axis is referred. Despite sealing along an inner surface, one advantage thereof is that a one-piece seal head may be used so as to minimize the danger of microchannels. Above all, this implies the advantage of obtaining the desired sealing property in this area even with greater tolerances, e.g., above 0.5 mm up to 2.5 mm.
Further advantageous features will be apparent in the following description and the same applies to the process measures for the production of the package.